In a modular tooling system, for example, of the type disclosed in U.S. Pat. No. 4,828,240 issued to the assignee of the present invention, it is frequently desirable to provide for supporting a workpiece at a predetermined angle relative to the movable table of a machine tool. Some workpieces may be positioned at a particular angle relative to the workpiece table by using an angular adjustment plate as shown in FIGS. 9 and 10 and described in column 5 of the above patent. However, sometimes it is necessary to position a workpiece at an inclined angle relative to a modular base plate having a precision X-Y grid pattern of threaded holes and precision bores with parallel axes. While an adjustable angle or sine plate, for example, as disclosed in U.S. Pat. No. 2,771,821, U.S. Pat. No. 3,788,633 and U.S. Pat. No. 2,816,489, may be used for this purpose, it is desirable to have an angular locating or positioning system which is simple and easy to use, especially with a modular tooling system. It is also desirable for the system to provide for quickly and accurately positioning a workpiece at a desired angle relative to the table and for positively securing the workpiece at the selected angle so that the workpiece may be accurately machined without vibration.